Fuel-cooling system

ABSTRACT

This disclosure describes a fuel-cooling system for cooling the liquid fuel in the system to avoid vapor lock. According to the specific embodiment disclosed, a fuel injection nozzle injects fuel into an intake tube which is connected to an intake manifold. The fuel so injected vaporizes. A fuel-cooling jacket surrounds the intake tube and liquid fuel is passed therethrough. The liquid fuel passing through the cooling jacket is cooled by the latent heat of vaporization from the vaporized fuel within the intake tube.

United States Patent Inventor Stuart (1. Hilborn 2,635,597 4/1953123/119 South Laguna.Calil. 2,869.527 1/1959 123/119 AppltNo. 821,9133.l18,492 1/1964 123/136X Filed May 5,1969 3.187.732 6/1965 123/119Patented July 20,1971 1 3,314,665 4/1967 123/136 X Assignee FuelInjection Engineering Company 3,473,523 10/1969 Hilborn 123/1 19 X SmnhLaguna Primary Erunu'ner- Laurence M. Goodridge Attorney-Smyth. Roston &Pavitt FUEL-CO0L1NG SYSTEM 24 Claims, 3 Drawing Figs.

US. Cl 123/119 R, ABSTRACT; This disdosure d -ib a f |i System 23/139,123/139 261/160, 1213/4131 forcooling the liquid fuel in the system toavoid vapor lock. Int. Cl F02d 3/04 According to h ifi embodimentdisdosei a f l injec Field of Search 123/1 19, {ion nozzle injects finto an intake tube which is connected 32; 261/190 to an intakemanifold. The fuel so injected vaporizes. A fuel- References Citedcooling jacket surrounds the intake tube and liquid fuel is passedtherethrough. The liquid fuel passing through the cool- UNITED STATESPATENTS ing jacket is cooled by the latent heat of vaporization from the1,953,809 4/1934 Kenneweg 261/160 vaporized fuel within the intake tubeFUEL-COOLING SYSTEM BACKGROUND OF THE INVENTION Under certain conditionsthe operation of an internal combustion engine can become greatlyimpaired due to excessive temperatures in the fuel system. Suchexcessive temperatures create gas bubbles in the fuel which causes thefamiliar vapor lock condition.

The vapor lock problem is magnified by high ambient air temperatures,poor cooling of the engine compartment, operation of the engine at highaltitude, poor design and in stallation of the fuel system, and by usinga fuel which contains low boiling point fractions. High-performanceengines such as racing engines are more likely to develop vapor lockbecause they have a higher heat output and they are generally installedin lightweight, close-fitting vehicle bodies where good ventilation isdifficult to obtain. ln addition, fuel injection systems which aregenerally used on high-performance engines are more sensitive thancarburetors to the vapor lock condition.

SUMMARY OF THE INVENTION The present invention solves the vapor lockproblem through the provision of a fuel-cooling system. Anotheradvantage of the present invention is that it results in a small gain inhorsepower particularly at higher r.p.m.'s where the fuel flow to theengine is large. Although the fuel-cooling system of this invention canbe used with different types of fuel systems it is particularly adaptedfor use with a fuel injection system.

In the typical fuel injection system, a fuel injection nozzle injectsfuel into the intake manifold downstream of the throttle valve. The fuelis atomized before or 'upon injection, and the heat within the intakemanifold causes vaporization of the atomized fuel. The present inventionmakes use of the latent heat of vaporization of the injected fuel bypassing at least some of the liquid fuel in the system in heat exchangerelation with the vaporized fuel to cool the liquid fuel and therebyprevent vapor lock.

An intake tube is connected to the intake manifold for conducting air tothe intake manifold. Contrary to the usual practice, the presentinvention provides a fuel injection nozzle upstream of the throttlevalve and mounted on the intake tube. The heat exchanger is preferablyin the form of a fuel cooling jacket which surrounds the intake tube. Totake advantage of the heat of vaporization, substantially all of thefuel-cooling jacket should be downstream of the fuel injection nozzle onthe intake tube.

Although coils may be used for the heat exchanger, it is preferred touse a cooling jacket because the cooling jacket is of simplerconstruction. To assure that the fuel will pass through the full lengthof the fuel-cooling jacket, the inlet and outlet therefor should be atopposite ends of the jacket. Each of the intake tubes can have afuel-cooling jacket, and the fuel can be passed from one fuel-coolingjacket to another to thereby obtain a maximum amount of cooling.Preferably, the inlet to the fuel-cooling jacket is below the outlet sothat the jacket will always be full of fuel. This arrangement alsocauses the heat exchanger to be of the counterflow type.

For best results, the fuel system should include a dual set of nozzlesfor each cylinder with the second or lower nozzle being downstream ofthe throttle valve. Although the lower nozzle for each engine cylindercan be deleted, this will result in an engine that runs poorly whenidling, at low speeds, and at part throttle. Alternatively, the throttlevalve can be raised above the upper nozzle, i.e., the nozzle adjacentthe fuel-cooling jacket, and the lower nozzle can be eliminated.However, this construction is rather cumbersome, and accordingly, a dualset of nozzles is preferred for each engine cylinder.

When the engine is operating, the intake manifold becomes very hot. Thepresent invention teaches that for optimum fuel cooling, the heatexchanger should be insulated from the intake manifold. Preferably thisis accomplished by joining the intake tube to the inlet manifold with aheat-insulating coupling. The coupling provides a heat-insulatingbarrier between the intake tube and the intake manifold to avoid directheat conduction therebetween. By using a resilient material for thecoupling, heat insulation and vibration damping can both be obtained. Tofurther optimize results, the fuelcooling jacket should be covered withinsulating material to avoid a heat gain from the air surrounding thefuel-cooling jacket.

The formation of some vapors in the liquid fuel in a fuel system isinherent notwithstanding the provision of a fuelcooling system. Thepresent invention minimizes the forma' tion of these vapors through theprovision ofa highly efficient fuel-cooling system. However, toeliminate any of the inherently formed vapors in the fuel stream, thepresent invention also provides means for separating such vapors fromthe liquid fuel. Preferably such vapor separation occurs after thefuel-cooling operation has at least begun. I

The fuel pump for most fuel injection systems will, at times, supplymore fuel than the engine can efficiently use. For this reason, manyfuel injection stems provide one or more bypasses for bypassing theexcess fuel supplied by the fuel injection pump. Such excess fuel isnormally bypassed back to the main fuel tank. The fuel injection pumpadds some heat to the fuel pumped thereby and is the location at whichgas bubbles are most likely to form in amounts which may be troublesome.Accordingly, the fuel-cooling operation and/or the vapor separationoperation preferably occur at a location in the fuel system which isupstream of the fuel pump.

If the excess fuel supplied by the pump were returned to the main fueltank, the cooling effect thereof would be lost in the main fuel tank asthis tank would contain a large quantity of fuel in relation to the coolbypassed fuel which would be supplied thereto. To overcome thedisadvantage accompanying the loss of the cooled bypassed fuel, thepresent invention provides a secondary fuel tank which receives the coolbypassed fuel. The secondary fuel tank is smaller than the main fueltank and preferably only contains cool fuel so that substantially noneof the cooling already obtained is lost. Actually the secondary fueltank may be large, if desired, but the quantity of fuel which it iscapable of holding should be small in relation to the quantity of fuelwhich can be retained in the main fuel tank. In this manner, the coolingeffect obtained from the cooling system can be concentrated on arelatively small amount of fuel with the main fuel tanlc supplying onlythe ad ditional fuel as is necessary to keep the level of fuel in thesecondary fuel tank at the desired level.

As the fuel injection pump is the location at which vapor lock is mostlikely to occur, the secondary fuel tank is preferably upstream of thepump so that the latter can take advantage of the cool fuel therein. Ina preferred form of the inventiqn, the secondary fuel tank liesdownstream of the fuelcooling means and upstream of the fuel injectionpump with the fuel-cooling means being as close to the pump as possibleso that the fuel flowing to the pump will be as cool as possible. Thesecondary fuel tank is elevated above the pump intake to keep the pumpwell primed. [n a preferred form of the invention, fuel is supplied fromthe main fuel tank through a first bank of heat exchangers to thesecondary fuel tank. The fuel injection pump supplies fuel from thesecondary fuel tank to the main injection nozzle. A bypass is located onthe discharge side of the fuel injection pump for bypassing fuel bank tothe secondary fuel tank through a second bank of heat exchangers.

The advantages of the secondary fuel tank and vapor separation can bemost efficiently accomplished by merely venting of the secondary fueltank. In a preferred form of the invention, the maximum fuel level inthe secondary fuel tank is controlled by a standpipe into which excessfuel can drain and flow by gravity back to the main fuel tank.

The invention, both as to its organization and method of operationtogether with further features and advantages thereof may best beunderstood by reference to the following description taken in connectionwith the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary, partiallydiagrammatic side elevational view partially in section of afuel-cooling system constructed inaccordance with the teachings of thisinvention. The portion of FIG. 1 which is shown in section is shown inradial cross section.

FIG. 2 is a fragmentary elevational view ofa second form of fuel-coolingsystem.

FIG. 3 is diagrammatic view of a fuel injection system constructed inaccordance with the teachings of this invention.

DESCRIPTION OF THE EMBODIMENT Referring to the drawing and in particularto FIG. 1, reference numeral 11 designates a fuel-cooling systemconstructed in accordance with the teachings of this invention. Thesystem 11 includes an injector or intake manifold 13 connectable to anengine (not shown), an intake tube in the form of a ram tube 15connected to the intake manifold by a coupling 17, a main fuel injectionnozzle 19, an auxiliary fuel injection nozzle 21, and a fuel coolingjacket 23,

The intake manifold 13 has a wall defining a passage 27 extendingtherethrough for the purpose of supplying fuel and air to one cylinderof the engine. A throttle valve in the form of a butterfly valve 29 ismounted within the passage 27 to control the flow of fluid therethroughto the engine.

Although other constructions can be used, in the embodiment illustrated,the wall 25 defines an auxiliary manifold passage 31 which leads from alocation within the passage 27 upstream of the butterfly valve 29 to thenozzle 19. Although other kinds of nozzles can be used, in theembodiment illustrated, the main fuel injection nozzle 19 is of theairgap type, such airgap type of nozzle being fully described inapplicant's copending application Ser. No. 560,538 now US. Pat. No.3,519,407. Generally, the airgap nozzle 19 has a fuel inlet 33 which isconnected to the fuel supply system and a plurality of air inlets in theform of radially extending ports 35 which communicate with the auxiliaryinjector passage 31. As described in said copending application, airenters the ports 35 and forms a tubular column around the fuel stream,and the air and fuel stream are simultaneously directed against adeflector surface 37 of the nozzle 19. As shown in FIG. 1 the deflectorsurface 37 lies within the passage 27 downstream of the butterfly valve29. lmpingement of the fuel against the deflector surface 37 causes thefuel to atomize and to be directed downwardly toward the discharge endof the passage 27. The nozzle 19 projects through the auxiliary injectorpassage 31 and the wall 25 and is mounted on the wall 25 by cooperatingthreads on the nozzle and the wall and by a nut 38 which is threadedonto the nozzle and into engagement with the outer surface of themanifold 13.

The intake manifold 13 has a tubular manifold extension 39 whichprovides a coaxial continuation of the passage 27. Although theextension 39 may be mounted on the manifold 13 in any suitable manner,in the embodiment illustrated, nut and bolt fasteners 41 project throughflanges 43 and 45, respectively, of the manifold 13 and the extension39.

The ram tube 15 is tubular and has a wall 47 which defines a generallycylindrical ram tube passage 49 which is coaxial with the passage 27.The ram tube passage 49 has an inlet 51 and the wall 47 is flaredoutwardly adjacent the inlet 51 to increase the diameter of the passage49. The wall 47 is preferably constructed of a material having high heatconductivity such as metal and to further improve heat conductivitythrough the wall 47, the region thereof adjacent the fuel-cooling jacket23 should be of minimum thickness. In operation air enters the inlet 51of the ram tube 15 and passes through the passage 49 toward the outlet52 of the passage 49.

The ram tube 15 and the extension 39 have confronting ends 53 and 55,respectively, which are held in spaced confronting relationship by thecoupling 17. During the operation of the engine, the manifold 13 and theextension 39 become very hot. By providing an insulating barrier 56between the confronting ends 53 and 55, heat conduction to the ram tube15 is substantially reduced.

The coupling 17 may be virtually any type which provides aheat-insulating barrier between the injector extension 39 and the ramtube 15. In the embodiment illustrated, the coupling 17 includes aheat-insulating member in the form of a resilient cylindrical band 57constructed of rubber and embracing the portions of the ram tube 15 andthe extension 39 adjacent the ends 53 and 55. The band 57 preferably hasa circumferential flange 56 lying between and engaging ends 53 and 55 toform a heat-insulating barrier. The band 57 preferably tightly grips theintake tube 15 and the extension 39. Although any heat-insulatingmaterial having suitable connector qualities may be utilized, it ispreferred to construct the band 57 of rubber because it is a goodinsulator and is sufficiently resilient to provide vibration damping.

The coupling 17 also includes an outer tightening band 59 which, in theembodiment illustrated, is constructed of metal. The band 59circumscribes the band 57 and has a pair of confronting flanges 6]through which a suitable fastener 63 such as a nut and bolt project topermit drawing of the flanges 61 toward each other with consequentcircumferential tightening of the band 59. In this fashion, the band 59serves to tighten the band 57 about the end portions of the ram tube 15and the extension 39. The band 59 in the embodiment illustrated issufficiently resilient to permit installing it about the band 57. Themetal band 59 is held out of engagement with the ram tube 15 and theextension 39 by the insulating band 57.

The auxiliary injection nozzle 21 is mounted on the ram tube 15 adjacentthe inlet thereof. The auxiliary nozzle 21 has a fuel inlet 65 and adeflector surface 67 within the passage 49. The auxiliary nozzle 21 inthe embodiment illustrated is not of the airgap type. The nozzle 21projects through a threaded aperture 69 in the wall 47 and is threadedlysecured therein. In addition, a nut 71 is threaded on to the exterior ofthe nozzle 21 and into engagement with a boss 73 to rigidly mount thenozzle 21 on to the ram tube 15.

The auxiliary nozzle 21 receives fuel from the inlet 65 and directs itas a stream against the deflector surface 67 which initiates atomizationof the fuel and directs the fuel downwardly (as shown in FIG. 1) towardthe outlet of the ram tube 15. As the fuel travels through the ram tube15 toward the outlet thereof, it vaporizes thereby cooling the airstreamwithin the passage 49, The cool air within the passage 49 cools the wall47 of the ram tube.

The cooling jacket 23 in the embodiment illustrated includes an outercylindrical wall 75, an upper wall 77, a lower wall 79 and a portion ofthe wall 47. A jacket 81 of insulating material completely encases thewall 75, 77 and 79 to minimize heat transfer therethrough.

The walls 75, 77, 79 and 47 define a tubular chamber 83 having an inlet85 and an outlet 87. The inlet 85 is preferably connected to the fuelsystem at a location therein so that all the liquid fuel pumped by thefuel pump will pass therethrough. The chamber 83 preferably has aminimum radial dimension to thereby increase the ratio of cooling areato volume of fuel with consequent improvement in the heat transfercharacteristics between the liquid fuel in the chamber 83 and thevaporized fuel within the passage 49. The chamber 83 preferably liesdownstream of the nozzle 21. Stated differently, the most effective heattransfer will occur downstream of the deflector 67 of the nozzle 21although the chamber 83 may project upstream thereof, if desired.

To assure that the liquid fuel will travel through a substantial portionof the chamber 83, the inlet 85 and the outlet 87 are preferably spacedsubstantially axially of the chamber 83. In the embodiment illustrated,the inlet 85 is located at the downstream end or lower end of thechamber 83 while the outlet 87 is located at the upstream end or lowerend of the chamber 83. The inlet 85 and the outlet 87 in the embodimentillustrated are spaced 180 circumferentially to thereby further increasethe length of the flow path through the chamber 83.

In an engine, one of the ram tubes 51 is provided for each of thecylinders. In the form shown in FIG. 1, the ram tube 51 is shown indetail, it being understood that the other ram tubes and cooperatingcomponents of the system are identical for each of the remainingcylinders of the engine. Thus, the ram tube 51 lies adjacent anidentical ram tube 51a having a cooling jacket 23a mounted thereon. Thejacket 23a has an inlet 85a and an outlet 870 with the outlet 87a beingillustrated 180 from its true position. A tube 89 interconnects theoutlet 87 of the cooling jacket 23 with the inlet 85a of the coolingjacket 230. In this fashion, the liquid fuel is first passed through thecooling jacket 23 and then passed in sequence through each of the othercooling jackets beginning with the cooling jacket 23a.

In operation of the system shown in FIG. 1, fuel under most operatingconditions is supplied to the main nozzle 19 and the auxiliary nozzle21. The nozzles 19 and 21 inject the fuel supplied thereto into themanifold 13 and the ram tube 15, respectively, with the fuel injectedinto the ram tube vaporiz' ing as it moves from the nozzle 21 toward theoutlet 52 of the ram tube. The fuel from the two nozzles is supplied tothe engine in a conventional manner with some of the fuel and air fromthe ram tube passing through the auxiliary manifold passage 31 into theports 35 of the nozzle 19 for injection by the latter into the manifold13. During idle or part throttle, there may be no fuel supplied by thenozzle 21 to the ram tube 15; however, for most high-performanceengines, such as racing engines, this condition exists for only a smallportion of the time that the engine is operating.

The latent heat of vaporization from the vaporized fuel in the passage49 cools the air in this passage and the cool air in turn cools the wall47 of the ram tube. Simultaneously, liquid fuel is supplied through theinlet 85 into the chamber 83. The cool wall 47 cools the liquid fuelflowing from the inlet 85 to the outlet 87 of the cooling jacket 23. Theliquid fuel is then conducted via the tube 89 into the cooling jacket 23of the adjacent ram tube 51a. The fuel is passed progressively throughthe remaining fuel-cooling jackets and may then reenter the fuel systemat a suitable location. After passing through all of the fuel-coolingjackets, the fuel is at a sufficiently low temperature so as to preventvapor lock even under severe operating conditions.

FIG. 2 illustrates a fuel-cooling system 101 which is identical to thefuel-cooling system 11 except that the former has an intake tube in theform of a sleeve 103 in lieu of the ram tube 51. The sleeve 103 isconnected to a manifold 105 which is supplied with air by a supercharger107 through a conduit 109. Several of the sleeves 103 are supplied withair from the manifold 105 and, if desired, a second manifold may beprovided to supply air to a second set of the sleeves for a second groupof engine cylinders. The fuel-cooling system 101 has an auxiliaryinjection nozzle 111, a fuel-cooling jacket 113, a coupling 115, anintake manifold 117, an inlet 119 to the fuelcooling jacket 113 and anoutlet 121 as well as all of the other components described hereinabovewith reference to FIG. 1.

The fuel-cooling system of this invention may be used with manydifferent kinds of fuel systems. However, it is particularly adapted foruse in a fuel injection system of the type shown in FIG. 3.

FIG. 3 illustrates a fuel injection system 151 which includes arelatively large main fuel tank 153 containing liquid fuel which issupplied by a relatively small electric motor operated supply pump 155through a conduit 157 to an engine 159. The engine 159 has fourfuel-cooling jackets 161 and four additional fuel-cooling jackets 163with one of the fuel-cooling jackets being provided for each cylinder ofthe engine. Although other kinds of fuel-cooling means may be used, thefuel-cooling jackets 161 and 163 are preferably of the type shown indetail in FIG. 1.

The fuel from the conduit 157 is passed in series through each of thefour fuel-cooling jackets 161 with the piping arrangement being of thetype shown in FIG. 1 to provide flow throughout the full length of eachof the fuel'cooling jackets 161. From the fuel-cooling jackets 161, thefuel flows through a conduit 165 into the upper end ofa secondary fueltank 167. The secondary fuel tank is quite small relative to the mainfuel tank and contains a vent opening 169 at the upper end thereofthrough which vapors from the fuel in the secondary fuel tank 167 canescape.

To control the maximum fuel level within the secondary fuel tank 167, astandpipe 171 is provided within the secondary fuel tank. The standpipe171 is a hollow tube having an open upper end through which liquid fuelin the secondary fuel tank 167 can pass if the fuel level rises abovethe upper end of the standpipe. Thus, the maximum fuel level within thesecondary fuel tank is controlled by the height of the upper end of thestandpipe 171.

The bottom of the secondary fuel tank 167 lies above the main fuel tank153. Accordingly, gravity flow of any excess fuel within the secondaryfuel tank can occur through a conduit 173 which connects the lower endof the standpipe 171 with the upper end of the main fuel tank 153. Thebottom of the tank 167 also lies above the intake ofa fuel injectionpump 175.

Fuel is drawn from the secondary fuel tank by the fuel injection pump175 and pumped through a metering valve 177 to the injection nozzles 19and 21 (FIG. 1). The injection pump 175 will, under most operatingconditions, pump more fuel than the engine 159 can effectively utilize.For this reason, it is necessary in many fuel injection systems toprovide one or more bypasses for bypassing such excess fuel back to thefuel tank. In the embodiment illustrated, a primary bypass I79 and asecondary bypass 181 are illustrated. it being understood that thesebypasses are purely exemplary and other types of bypasses may beutilized.

The primary bypass 179 is provided to permit the driver to manually varythe amount of fuel bypassed therethrough depending upon the type of fuelwhich is being burned and the desired fuel/air ratio. To this end theprimary bypass 179 includes a manual selector valve 183 and threeorifices or jets 1840, 184b and 184c of different sizes with theselector valve being manually operable to selectively direct flowthrough any of the jets. Of course other types of primary bypasses maybe used.

The metering valve 177 is controlled in conventional fashion by alinkage from the throttle, and the metering valve 177 may be of the typewhich bypasses an increasing amount of fuel through the secondary bypass181 as the metering valve reduces the fuel flow to the main injectionnozzle. The secondary bypass 181 includes a valve 185 which ispreferably a spring-loaded check valve which opens at a preselectedfuelpressure to permit flow through the secondary bypass 181.

The bypassed fuel from the primary bypass 179 and the secondary bypass181 is then passed through the fuel-cooling jackets 163 in the mannerdescribed hereinabove with reference to FIG. 1. The bypassed fuel thenflows back to the secondary fuel tank 167.

The fuel passing through the metering valve 177 flows to the main fuelinjection nozzles through a conduit 187 or to the auxiliary fuelinjection nozzles through a conduit 189 and a valve 191. The valve 191is a spring-loaded check valve which opens at a preselected fuelpressure to permit fuel flow to the auxiliary nozzles.

By way of example, the fuel system of FIG. 3 may be similar to the fuelinjection system shown in applicant's copending application Ser. No.754,752 now US. Pat. No. 3,473,523. Specifically, the metering valve177, the pump 175, the primary bypass 179 and the secondary bypass 181may be identical to the corresponding components of the system shown insaid copending application.

In operation of the system 151 of FIG. 3, fuel is supplied from the mainfuel tank 153 through the fuel-cooling jackets 16] in which thetemperature of the fuel is reduced by the latent heat of vaporization ofthe fuel in the intake tubes for such fuel-cooling jackets. The coolliquid fuel is then passed through the conduit 165 into the secondaryfuel tank 167 and any vapors within the liquid fuel are allowed toescape through the vent opening 169.

Fuel is drawn from the secondary fuel tank 167 by the injection pump 175and fed to the injection nozzles as permitted by the metering valve 177with any excess fuel flowing through the bypasses 179 and 181 to thefuel-cooling jackets 163 where such excess fuel is cooled by the latentheat of vaporization of the vaporized fuel in the corresponding intaketubes. Cooling of the excess fuel in the fuel-cooling jackets 163 isdesirable to eliminate any heat gain which may have occurred in suchfuel as a result of its passing through the injection pump 175. Theexcess fuel is returned to the secondary fuel tank and thus, only fuelwhich has passed through at least one of the cooling jackets 161 or 163is fed to the secondary fuel tank. In this manner only relatively coolfuel is retained in the secondary fuel tank.

Although exemplary embodiments of the invention have been shown anddescribed, many changes, modifications, and substitutions may be made byone having ordinary skill in the art without necessarily departing fromthe spirit and scope of this invention.

lclaim:

l. A fuel injection system for supplying fuel from a fuel source to anintake manifold of an engine comprising:

an intake tube forming an extension of the intake manifold for supplyingair to the intake manifold;

first and second fuel injection nozzles mounted, respectively, on theintake manifold and the intake tube;

conduit means for connecting said first and second fuel injectionnozzles to the fuel source;

pump means for supplying fuel through said conduit means to said nozzlesto cause the nozzles to inject fuel into the intake manifold and theintake tube, respectively, whereby the fuel injected into said intaketube vaporizes, the fuel injected by said nozzles constituting a primaryfuel supply, said pump means supplying fuel to said first nozzle atvarious engine operating conditions including nonidling conditions; and

means defining a fuel-cooling jacket extending at least part way aroundsaid intake tube, at least a substantial portion of said cooling jacketlying downstream of said second nozzle, said cooling jacket forming aportion of said conduit means so that at least some of the fuel from thefuel source including at least a substantial portion of said primaryfuel supply can flow therethrough in heat exchange relationship with thefuel in said intake tube whereby the latent heat of vaporization fromthe fuel in said intake tube cools said portion of the primary fuelsupply as it flows through said coolingjacket.

2. A fuel injection system as defined in claim 1 wherein saidfuel-cooling jacket has an inlet for receiving fuel from the fuel sourceand an outlet, said fuel-cooling jacket having first and second endportions, said inlet and said outlet being located closely adjacent saidfirst and second end portions, respectively, whereby the fuel must flowsubstantially completely through said cooling jacket in traveling fromsaid inlet to said outlet.

3. A fuel injection system as defined in claim 1 including couplingmeans for connecting said intake tube to said intake manifold, saidcoupling means providing a heat-insulating barrier to minimize heattransfer between the intake manifold and the intake tube.

4. A fuel injection system as defined in claim 3 wherein saidfuel-cooling jacket completely surrounds said intake tube and saidsecond fuel injection nozzle is mounted at the end thereof remote fromsaid intake manifold, said fuel-cooling jacket having an inlet and anoutlet located at opposite ends of said fuel-cooling jacket, and saidfuel-cooling jacket being surrounded by an insulating jacket constructedof heat-insulating material.

5. A fuel injection system as defined in claim 1 wherein said intaketube includes a ram tube.

6. A fuel injection system as defined in claim 1 including asupercharger and means for connecting the intake tube to thesupercharger.

7. A fuel-cooling system for use in a fuel system for supplying fuel toan engine, said fuel-cooling system comprising:

first and second conduits for supplying air to first and secondcylinders of the engine;

first and second fuel injection nozzles mounted, respective ly, on saidfirst and second conduits to inject fuel into said conduits, the fuelinjected by said fuel injection nozzles into said conduits vaporizing tocool the air in the com duits and the conduits;

first and second fuel-cooling jackets surrounding said first and secondconduits, respectively, at least a substantial portion of each of saidfuel-cooling jackets lying downstream of its respective fuel injectionnozzle, eachof said fuel-cooling jackets having upstream and downstreamend portions with the downstream end portion being downstream of theassociated fuel injection nozzle;

said first fuel-cooling jacket having an inlet closely adjacent one endportion thereof and an outlet closely adjacent the other end portionthereof, said inlet being connectable to the fuel system to receive fueltherefrom;

said second fuel-cooling jacket having an inlet closely adjacent one endportion thereof and an outlet closely adjacent said other end portionthereof; and

conduit means extending between said outlet of said first fuel-coolingjacket and said inlet of said second fuel-cooling jacket for providing afuel passage between said fuelcooling jackets whereby the fuel suppliedto said inlet is cooled by the vaporization of fuel in the conduits andthe fuel is required to flow substantially completely through the fulllength of each of said first and second fuel-cooling jackets.

8. A fuel-cooling system as defined in claim 7 wherein said other endportion of said first fuel-cooling jacket is said upstream end portionand said one end portion of said second fuel-coolingjacket is saiddownstream end portion thereof.

9. A fuel-cooling system as defined in claim 7 including aheat-insulating jacket surrounding at least one of saidfuelcoolingjackets.

10. A fuel-cooling system as defined in claim 7 wherein said firstconduit includes an intake tube, said intake tube being connectable toan intake manifold of the engine, said fuelcooling system includingcoupling means for connecting said intake tube to the intake manifold,said coupling providing a heat-insulating barrier between said intaketube and the intake manifold to thereby minimize heat transfer from theintake manifold to the intake tube.

ll. A fuel injection system for conducting fuel from a fuel source to anengine comprising:

means for directing fuel into the engine;

conduit means for conducting fuel from the fuel source to said means fordirecting;

means for supplying the fuel from the fuel source through said conduitmeans to the engine; fuel-cooling means downstream of the fuel sourceand upstream of said means for directing for cooling at least some ofthe fuel supplied by said means for supplying;

said means for supplying including a fuel injection pump downstream ofsaid fuel-cooling means;

a secondary fuel tank upstream of said fuel injection pump;

and

bypass means downstream of said fuel-cooling means for bypassing atleast some of any excess fuel pumped by said fuel injection pump intosaid secondary fuel tank while the engine runs, said fuel injection pumppumping the fuel from the secondary fuel tank to said means fordirecting.

l2. A fuel injection system as defined in claim 11 including means forlimiting the maximum quantity of fuel which can be contained in thesecondary fuel tank to an amount less than the amount which iscontainable at said source.

13. A fuel injection system as defined in claim ll including meansupstream of said fuel injection pump for separating any vapors in thefuel supplied thereto.

14. A fuel injection system as defined in claim I] wherein saidsecondary fuel tank is downstream of said fuel-cooling means.

15. A fuel injection system as defined in claim I] wherein the bottom ofsaid secondary fuel tank is at an elevation above said fuel injectionpump whereby the fuel injection pump is kept well primed.

16. A fuel injection system for an engine having a plurality ofcylinders comprising:

a main fuel tank adapted to contain fuel for operating the engine;

a plurality of intake conduits mounted on said engine for supplying airthereto, one of said intake conduits being provided for each of saidcylinders of the engine;

means for directing fuel into each of said intake conduits,

the fuel in each of said intake conduits vaporizing;

a plurality of heat exchangers mounted, respectively, in exchangerelationship with at least some of said intake conduits;

a secondary fuel tank adapted to contain fuel, said secondary fuel tankbeing capable of containing less fuel than said main fuel tank;

means for supplying fuel from said main fuel tank through at least oneof said heat exchangers to said secondary fuel tank, the heat ofvaporization of the vaporized fuel in the intake conduit cooling thefuel in said one heat exchanger;

a fuel pump for pumping fuel from said secondary fuel tank to said meansfor directing, said fuel pump being downstream of said secondary fueltank;

bypass means on the discharge side of said fuel pump for directingexcess fuel through at least another of said heat exchangers to coolsuch excess fuel; and

means for returning at least some of the excess fuel from said anotherheat exchanger to the secondary fuel tank.

17. A fuel injection system as defined in claim 16 wherein said meansfor directing includes a main nozzle and an auxiliary nozzle for each ofsaid intake conduits, said system including a metering valve downstreamof said pump for controlling fuel fiow to said nozzles.

18. A fuel injection system as defined in claim 16 wherein saidsecondary fuel tank lies above said main fuel tank, said systemincluding a standpipe in said secondary fuel tank for limiting themaximum amount of fuel that can be contained therein and for initiatinggravity flow of any fuel in excess of said maximum amount back to saidmain fuel tank.

19. A fuel injection system as defined in claim 16 wherein saidsecondary fuel tank is vented to provide for vapor separation of anyvapors in the fuel supplied thereto.

20. A fuel injection system for conducting fuel from a fuel source to anengine comprising:

means for directing fuel into the engine;

conduit means for conducting fuel from the fuel source to said means fordirecting;

means for supplying the fuel from the fuel source through said conduitmeans to the engine, said means for supplying including a fuel pump;

fuel-cooling means for cooling at least some of the fuel in said conduitmeans; and

a secondary fuel tank for receiving at least some of the fuel cooled bysaid fuel-cooling means when the engine is running, said fuel pump beingsupplied with fuel from said secondary fuel tank.

21. A fuel injection system for supplying fuel from a fuel source to anengine comprising:

means for directing fuel into the engine;

fuel-cooling means upstream of said means for directing and downstreamof said fuel source for cooling the fuel sup plied thereto; means forsupplying fuel from said fuel source through said fuel-cooling means toprovide relatively cool fuel;

a secondary fuel tank;

a conduit for supplying the relatively cool fuel from the fuelcoolingmeans to the secondary fuel tank when the engine is running;

pump means for supplying the relatively cool fuel from said secondaryfuel tank to said means for directing; and

said secondary fuel tank including means for separating any vapors whichmay exist in the fuel supplied thereto whereby the pump means receivesrelatively cool and relatively vapor free fuel.

22. A fuel injection system as defined in claim 21 wherein the fuel pumpis subject to pumping excess fuel and including means for returning atleast some of such excess fuel to the secondary fuel tank withoutpassing said some of such fuel through the fuel source.

23. A fuel-cooling system for use in a fuel system for supply ing fuelto an intake manifold of an engine comprising:

a ram tube having an open end for supplying air from said open end tothe engine;

a coupling for mounting the ram tube on the intake manifold, saidcoupling providing a heat-insulating barrier between said intakemanifold and the ram tube to reduce heat conduction from the intakemanifold to the ram tube and being constructed at least in part of aheat insulating material to thereby further reduce heat conduction fromthe intake manifold to the ram tube;

a heat exchanger in heat exchange relationship with said ram tube, saidheat exchanger being connectable to the fuel system so that fuel fromthe system can pass therethrough; and

a fuel injection nozzle for supplying fuel to the ram tube at apredetermined location therein, the fuel being vaporized in said ramtube, the latent heat of vaporization of the vaporized fuel cooling theram tube, at least a portion of said heat exchanger means beingdownstream of said fuel injection noule whereby the fuel in said heatexchanger is cooled by the heat of vaporization of the fuel in said ramtube.

24. A fuel cooling system as defined in claim 23 wherein said couplingincludes a band of heat-insulating material surrounding the adjacent endportions of the ram tube and the intake manifold, said band being inengagement with said end portions, said coupling including acircumferential flange of heat-insulating material lying between theadjacent ends of the ram tube and the intake manifold.

1. A fuel injection system for supplying fuel from a fuel source to anintake manifold of an engine comprising: an intake tube forming anextension of the intake manifold for supplying air to the intakemanifold; first and second fuel injection nozzles mounted, respectively,on the intake manifold and the intake tube; conduit Means for connectingsaid first and second fuel injection nozzles to the fuel source; pumpmeans for supplying fuel through said conduit means to said nozzles tocause the nozzles to inject fuel into the intake manifold and the intaketube, respectively, whereby the fuel injected into said intake tubevaporizes, the fuel injected by said nozzles constituting a primary fuelsupply, said pump means supplying fuel to said first nozzle at variousengine operating conditions including nonidling conditions; and meansdefining a fuel-cooling jacket extending at least part way around saidintake tube, at least a substantial portion of said cooling jacket lyingdownstream of said second nozzle, said cooling jacket forming a portionof said conduit means so that at least some of the fuel from the fuelsource including at least a substantial portion of said primary fuelsupply can flow therethrough in heat exchange relationship with the fuelin said intake tube whereby the latent heat of vaporization from thefuel in said intake tube cools said portion of the primary fuel supplyas it flows through said cooling jacket.
 2. A fuel injection system asdefined in claim 1 wherein said fuel-cooling jacket has an inlet forreceiving fuel from the fuel source and an outlet, said fuel-coolingjacket having first and second end portions, said inlet and said outletbeing located closely adjacent said first and second end portions,respectively, whereby the fuel must flow substantially completelythrough said cooling jacket in traveling from said inlet to said outlet.3. A fuel injection system as defined in claim 1 including couplingmeans for connecting said intake tube to said intake manifold, saidcoupling means providing a heat-insulating barrier to minimize heattransfer between the intake manifold and the intake tube.
 4. A fuelinjection system as defined in claim 3 wherein said fuel-cooling jacketcompletely surrounds said intake tube and said second fuel injectionnozzle is mounted at the end thereof remote from said intake manifold,said fuel-cooling jacket having an inlet and an outlet located atopposite ends of said fuel-cooling jacket, and said fuel-cooling jacketbeing surrounded by an insulating jacket constructed of heat-insulatingmaterial.
 5. A fuel injection system as defined in claim 1 wherein saidintake tube includes a ram tube.
 6. A fuel injection system as definedin claim 1 including a supercharger and means for connecting the intaketube to the supercharger.
 7. A fuel-cooling system for use in a fuelsystem for supplying fuel to an engine, said fuel-cooling systemcomprising: first and second conduits for supplying air to first andsecond cylinders of the engine; first and second fuel injection nozzlesmounted, respectively, on said first and second conduits to inject fuelinto said conduits, the fuel injected by said fuel injection nozzlesinto said conduits vaporizing to cool the air in the conduits and theconduits; first and second fuel-cooling jackets surrounding said firstand second conduits, respectively, at least a substantial portion ofeach of said fuel-cooling jackets lying downstream of its respectivefuel injection nozzle, each of said fuel-cooling jackets having upstreamand downstream end portions with the downstream end portion beingdownstream of the associated fuel injection nozzle; said firstfuel-cooling jacket having an inlet closely adjacent one end portionthereof and an outlet closely adjacent the other end portion thereof,said inlet being connectable to the fuel system to receive fueltherefrom; said second fuel-cooling jacket having an inlet closelyadjacent one end portion thereof and an outlet closely adjacent saidother end portion thereof; and conduit means extending between saidoutlet of said first fuel-cooling jacket and said inlet of said secondfuel-cooling jacket for providing a fuel passage between saidfuel-cooling jackets whereby the fuel supplied to said inlet is cooledby the vaporization of fuel in the conduits and the fuel is required toflow substantially completely through the full length of each of saidfirst and second fuel-cooling jackets.
 8. A fuel-cooling system asdefined in claim 7 wherein said other end portion of said firstfuel-cooling jacket is said upstream end portion and said one endportion of said second fuel-cooling jacket is said downstream endportion thereof.
 9. A fuel-cooling system as defined in claim 7including a heat-insulating jacket surrounding at least one of saidfuel-cooling jackets.
 10. A fuel-cooling system as defined in claim 7wherein said first conduit includes an intake tube, said intake tubebeing connectable to an intake manifold of the engine, said fuel-coolingsystem including coupling means for connecting said intake tube to theintake manifold, said coupling providing a heat-insulating barrierbetween said intake tube and the intake manifold to thereby minimizeheat transfer from the intake manifold to the intake tube.
 11. A fuelinjection system for conducting fuel from a fuel source to an enginecomprising: means for directing fuel into the engine; conduit means forconducting fuel from the fuel source to said means for directing; meansfor supplying the fuel from the fuel source through said conduit meansto the engine; fuel-cooling means downstream of the fuel source andupstream of said means for directing for cooling at least some of thefuel supplied by said means for supplying; said means for supplyingincluding a fuel injection pump downstream of said fuel-cooling means; asecondary fuel tank upstream of said fuel injection pump; and bypassmeans downstream of said fuel-cooling means for bypassing at least someof any excess fuel pumped by said fuel injection pump into saidsecondary fuel tank while the engine runs, said fuel injection pumppumping the fuel from the secondary fuel tank to said means fordirecting.
 12. A fuel injection system as defined in claim 11 includingmeans for limiting the maximum quantity of fuel which can be containedin the secondary fuel tank to an amount less than the amount which iscontainable at said source.
 13. A fuel injection system as defined inclaim 11 including means upstream of said fuel injection pump forseparating any vapors in the fuel supplied thereto.
 14. A fuel injectionsystem as defined in claim 11 wherein said secondary fuel tank isdownstream of said fuel-cooling means.
 15. A fuel injection system asdefined in claim 11 wherein the bottom of said secondary fuel tank is atan elevation above said fuel injection pump whereby the fuel injectionpump is kept well primed.
 16. A fuel injection system for an enginehaving a plurality of cylinders comprising: a main fuel tank adapted tocontain fuel for operating the engine; a plurality of intake conduitsmounted on said engine for supplying air thereto, one of said intakeconduits being provided for each of said cylinders of the engine; meansfor directing fuel into each of said intake conduits, the fuel in eachof said intake conduits vaporizing; a plurality of heat exchangersmounted, respectively, in exchange relationship with at least some ofsaid intake conduits; a secondary fuel tank adapted to contain fuel,said secondary fuel tank being capable of containing less fuel than saidmain fuel tank; means for supplying fuel from said main fuel tankthrough at least one of said heat exchangers to said secondary fueltank, the heat of vaporization of the vaporized fuel in the intakeconduit cooling the fuel in said one heat exchanger; a fuel pump forpumping fuel from said secondary fuel tank to said means for directing,said fuel pump being downstream of said secondary fuel tank; bypassmeans on the discharge side of said fuel pump for directing excess fuelthrough at least another of said heat exchangers to cool such excessfuel; and means for returning at least some of the excess fuel from saidanother heat exchanger to the secondary fuel tank.
 17. A fuel injectionsystem as defined in claim 16 wherein said means for directing includesa main nozzle and an auxiliary nozzle for each of said intake conduits,said system including a metering valve downstream of said pump forcontrolling fuel flow to said nozzles.
 18. A fuel injection system asdefined in claim 16 wherein said secondary fuel tank lies above saidmain fuel tank, said system including a standpipe in said secondary fueltank for limiting the maximum amount of fuel that can be containedtherein and for initiating gravity flow of any fuel in excess of saidmaximum amount back to said main fuel tank.
 19. A fuel injection systemas defined in claim 16 wherein said secondary fuel tank is vented toprovide for vapor separation of any vapors in the fuel supplied thereto.20. A fuel injection system for conducting fuel from a fuel source to anengine comprising: means for directing fuel into the engine; conduitmeans for conducting fuel from the fuel source to said means fordirecting; means for supplying the fuel from the fuel source throughsaid conduit means to the engine, said means for supplying including afuel pump; fuel-cooling means for cooling at least some of the fuel insaid conduit means; and a secondary fuel tank for receiving at leastsome of the fuel cooled by said fuel-cooling means when the engine isrunning, said fuel pump being supplied with fuel from said secondaryfuel tank.
 21. A fuel injection system for supplying fuel from a fuelsource to an engine comprising: means for directing fuel into theengine; fuel-cooling means upstream of said means for directing anddownstream of said fuel source for cooling the fuel supplied thereto;means for supplying fuel from said fuel source through said fuel-coolingmeans to provide relatively cool fuel; a secondary fuel tank; a conduitfor supplying the relatively cool fuel from the fuel-cooling means tothe secondary fuel tank when the engine is running; pump means forsupplying the relatively cool fuel from said secondary fuel tank to saidmeans for directing; and said secondary fuel tank including means forseparating any vapors which may exist in the fuel supplied theretowhereby the pump means receives relatively cool and relatively vaporfree fuel.
 22. A fuel injection system as defined in claim 21 whereinthe fuel pump is subject to pumping excess fuel and including means forreturning at least some of such excess fuel to the secondary fuel tankwithout passing said some of such fuel through the fuel source.
 23. Afuel-cooling system for use in a fuel system for supplying fuel to anintake manifold of an engine comprising: a ram tube having an open endfor supplying air from said open end to the engine; a coupling formounting the ram tube on the intake manifold, said coupling providing aheat-insulating barrier between said intake manifold and the ram tube toreduce heat conduction from the intake manifold to the ram tube andbeing constructed at least in part of a heat insulating material tothereby further reduce heat conduction from the intake manifold to theram tube; a heat exchanger in heat exchange relationship with said ramtube, said heat exchanger being connectable to the fuel system so thatfuel from the system can pass therethrough; and a fuel injection nozzlefor supplying fuel to the ram tube at a predetermined location therein,the fuel being vaporized in said ram tube, the latent heat ofvaporization of the vaporized fuel cooling the ram tube, at least aportion of said heat exchanger means being downstream of said fuelinjection nozzle whereby the fuel in said heat exchanger is cooled bythe heat of vaporization of the fuel in said ram tube.
 24. A fuelcooling system as defined in claim 23 wherein said coupling includes aband of heat-insulating material surrounding the adjacent end portionsof tHe ram tube and the intake manifold, said band being in engagementwith said end portions, said coupling including a circumferential flangeof heat-insulating material lying between the adjacent ends of the ramtube and the intake manifold.